Rechargeable batteries that Oximeter CMS50D+ use

Hi all

Googled and searched, seems like there's no writings about this, so decided to ask. May I know what brands of rechargeable batteries are you all using for Comtec CMS50D+?

Am using Eneloop AAA batteries, but I realised it doesn't last long, like only 10 hours (if it's freshly charged and used immediately), and less than 8 hrs (auto shut off) if it's stored for 1 day....

Googled and read up on batteries, learnt that alkaline batteries gives 1.5V charge, and eneloop is 1.2V. So when my 50D+ auto shutdown from "low battery", and the battery is measured using my battery charge meter, it just shows only a small drop (11 bars compared to 13 bars after freshly charged, which is still within the working range of my other equipment). Am not sure if 50D+ working range is higher than average appliance.

Working range (as stated from http://cms.contecmed.com/html/show-9-99-1.html)
Voltage: DC 2.6V～3.6V (Eneloop rechargeable is advertised as 1.2V, 2 batteries in parallel is = 2.4V), on googling, found that it start off from 1.4V (2.8V), then should maintain at 1.3V for first 25% of discharge (2.6V, bare minimum for 50D+), then after that it will go below 1.3V the next 75% (graph on http://s3.media.squarespace.com/product ... -curve.gif)


At first I thought it will last 24 hrs (site above says theoretically 32 hrs), so I can use it for 2-3 nights per charge. Now if I can't use it past 1 night (after storage), am not sure if my "new" rechargeable batteries is faulty, or......

Have also ordered these lithium batteries that's advertised as 1.5V, see if this works well
https://www.lazada.sg/products/aoyou-us ... c&search=1

Any advise appreciated! Thanks

A pulse oximeter will definitely be more sensitive to the voltage difference than, say, a TV remote. Not sure about that particular brand you linked to, but rechargeable Lithium is probably your best choice. Let us know how it works

Also note that like the Eneloop (NiMH), fully-charged batteries with different chemistry will also output a higher voltage than they are rated for. A fully charged 1.5V battery could output 1.8V for example. An Eneloop-style battery will always have a lower voltage than a similarly-charged Lithium or Alkaline battery.

I use plain old dollar store aaa non-rechargeable duracell batteries, replace as necessary and don't worry about volts and amps. never had a problem.

greatunclebill wrote: ↑

Mon Jun 25, 2018 10:59 am

I use plain old dollar store aaa non-rechargeable duracell batteries, replace as necessary and don't worry about volts and amps. never had a problem.

Good answer!

Or bulk packs of Duracell Batteries, if you wanted a rechargeable you should have bought a tester made for them. Jim

Lith Ion, not good idea voltage not right.

Goofproof wrote: ↑

Mon Jun 25, 2018 11:14 am

Lith Ion, not good idea voltage not right.

They're Lithium Polymer batteries. The voltage is correct.

I have the same pulse oximeter as the OP and have used Li-FeS batteries with it. The Polymer batteries will likely end up being cheaper than even bulk alkaline batteries over time.

Superball wrote: ↑

Mon Jun 25, 2018 12:18 am

A pulse oximeter will definitely be more sensitive to the voltage difference

No, because they're *designed* to work with varying voltages, due to the nature of the supply, and they internally regulate the power coming in.

palerider wrote: ↑

Mon Jun 25, 2018 12:06 pm

Superball wrote: ↑

Mon Jun 25, 2018 12:18 am

A pulse oximeter will definitely be more sensitive to the voltage difference

No, because they're *designed* to work with varying voltages, due to the nature of the supply, and they internally regulate the power coming in.

Sure, but I was talking about the minimum voltage they can run on. That'll be a lot higher for a pulse oximeter than for a TV remote.

Whatever that voltage is, an 1.2V NiMH battery will reach it a lot earlier than a 1.5V alkaline or lithium battery. Hence the poor performance of the Eneloop batteries the OP (and I, incidentally) experienced.

This may help shed some light on the difference between Alkaline and NiMh batteries...

http://eznec.com/Amateur/1.5_vs_1.2_Volt_Batteries.pdf

Alkalines start off at 1.5 volts and go down from there. NiMh has a mid point voltage of about 1.2 volts. If we want to rate a battery according to Alkaline ratings the the Alkaline is rated at 1.5 volts and the NiMh would be rated at 1.4 volts. If we want to rate according to the NiMh ratings the Alkaline batter would be rated at about 1.1 volts while the NiMh battery is rated at 1.2 volts.